We describe inertial effects in the dewetting of a low viscosity liquid (like water) deposited on hydrophobic solid substrates. The liquid dewets by nucleation and growth of a dry patch. We expect three regimes depending on the liquid viscosity, the film thickness and the static contact angle: (i) purely inertial (similar to the bursting of soap films); (ii) semi inertial, where dissipation occurs in a hydrodynamic boundary layer; (iii) purely viscous, for small contact angles, or very viscous liquids.